Which statement is true about neutrons?

The statement that neutrons determine the mass number is accurate because the mass number of an atom is defined as the total number of protons and neutrons in the nucleus. Since neutrons are neutral particles and do not carry a charge, they do not play a role in determining the chemical properties of an element, which are primarily influenced by the number of protons and electrons. While neutrons contribute to the overall mass of an atom, the presence or absence of neutrons can also give rise to different isotopes of an element, which have the same number of protons but different mass numbers due to varying numbers of neutrons.

In contrast, neutrons are not positively charged; they possess no charge. They are located within the nucleus of the atom, not outside it, which rules out the idea that they can be found externally. Lastly, neutrons are not the primary chemical property of an element; rather, it is the arrangement and number of electrons, particularly in the outer shell, that dictate chemical behavior.